1. Technical Field
This invention relates generally to metallic sliding bearings of the type in which a layer of bearing material is applied to a steel backing and supported by a component for journaling another relatively rotatable component, and more particularly to the manner of securing such bearings in use.
2. Related Art
Sliding bearings are used in many applications for journaling a relatively rotatable member. In the case of a connecting rod for internal combustion engines, the large end of the rod has a cylindrical bore and is split to provide a separable bearing cap for securing the large end about a relatively rotatable crankshaft of the engine. Typically, a set of half sliding bearings are installed in the bore with the convex outer surface of the steel backing of the half bearings seated against the concave wall of the bore and separated across the parting plane of the bearing cap. In a typical connecting rod, the bearing cap portion is bolted under high load to the companion upper half of the large end with sufficient force to clamp the half sliding bearings against movement relative to the connecting rod. To sustain such clamping force, high temper bolts must be used and sufficient material in the shoulder regions of the large end provided for supporting such clamping loads without failure of the connecting rod material. The need for high temper bolts and material mass adds to the cost, weight and size of connecting rods.
It has been proposed to permanently join half shells of porous sliding bearings to the bore surface of the large end of connecting rods by way of resistance welding or high temperature bonding to yield a substantially co-extensive metal bond across the full contact surfaces of the united parts. In U.S. Pat. No. 1,768,529, for example, the bearing shell and connecting rod are heated to an elevated temperature and the joining surfaces coated with tin which, upon cooling, unites the bearing to the connecting rod. In U.S. Pat. No. 1,957,111, the half bearing and connecting rod are heated to an elevated temperature sufficient to weld the bearing shell to the connecting rod across their contiguous contact surfaces without the use of a low temperature bonding metal, such as tin. In both cases, the bearing metal is subjected directly or indirectly to the heat of welding.
A combination of a component and a sliding bearing for supporting a member for rotation relative to the component according to a presently preferred embodiment of the invention comprises a metal backing of the sliding bearing having a convex outer surface extending longitudinally between opposite ends and laterally between opposite edge regions of the backing. At least one layer of a relatively softer bearing material is applied to a concave inner surface of the bearing. A concave seat of the component supports the convex outer surface of the metal backing. According to the invention, the backing is edge welded only along the edge regions to the component for securing the bearing to the component. The invention also contemplates a method of joining a sliding bearing to a component which involves edge welding the lateral edge portions only of the backing to the component defining edge welds which are spaced across a central region of the backing between the edge weld.
The invention has the advantage of enabling a modem sliding bearing to be secured permanently to a component by welding in a manner that does not subject the bearing material of the sliding bearing to the heat of welding. By securing the backing with only edge welds, a central region of the backing between the edge weld is not subjected to the heat of welding and thus the bearing material is isolated from such heat.
Isolating the bearing material from the heat of welding has the advantage of preserving the physical properties of the bearing metal. Known prior welding techniques which subject the entire sliding bearing, including the bearing material, to the heat of welding or joining, could alter or destroy any bearing layer materials which are commonly used in sliding bearing applications. Such bearing materials including, but are not limited to, aluminum alloys, cooper alloys, tin, lead, plastics and the like.
The invention has the farther advantage of enabling conventional backing and bearing layer materials to be used in the edge-welded bearing. Since the bearing material is protected against the heat of welding by provision of the edge welds, such conventional bearing metals as aluminum alloys, copper alloys, tin, lead, plastics, and the like can be employed and welded without concern for damage or loss of properties.
The invention has the further advantage of minimizing the clamping requirement in connecting rod and other applications where a bolted bearing cap is used. Since the sliding bearing is held in place by the edge welds and does not rely solely on the clamping force from the bearing cap bolts to hold the bearings in place in use, lighter, less costly bolts can be employed and less material can be provided to the shoulder regions of the components where the bolts are held.
The invention has the further advantage of simplifying the manufacture of component parts that have such sliding bearings by eliminating the need to final finish the surface of the concave bearing seat of the component prior to receiving the sliding bearing. The edge welds eliminate the need for such final finishing while providing the needed support to the sliding bearing in use.